Snow

Science Interests

marine biology
fish
skiing
the construction if the bases of skis
snow types
humidity in the winter
cardiovascular efficiency and limits
running
metals

Question

What temperatures do certain types of snow crystals form at?
How does the humidity and air tempeture affect the type of snow crystals?
Revised
When the enviorment that the dry ice and the wires are in is humid what happens differently in the formation of the crystials?

RESEARCH

I have found that there are several processes that snow goes through as it forms. one of those is at temperatures between below the freezing point of water snow begins in the atmosphere as water condenses into very small particles forming tiny droplets that freeze. This is called heterogenous nucleation. Because of the differences in saturation vapor pressure over ice versus water, these very small ice particals grow inside the cloud droplets and eventually grow six evenly spaced branches. As more and more water vapor becomes part of these branches, the ice crystal become heavier and begin to fall from the sky. The ice crystals encounter a very complex and variable atmospheric conditions, which contribute to its unique form. If the snow ctystal comes into contact with air warmer that freezing the crystal will begin to melt. This melting acts as an ahedsive causing crystals to bond together into larger flakes.The ice crystals that make up snowflakes are symmetrical because they are part of a internal order of the water molecules as they arrange themselves through the process of crystallization. During this process, water molecules align themselves into the most stable least demanding form by maximizing attractive forces and minimizing repelant ones.

I discovered this table of snowflakes and what temperatures they form at and their tipes.

• 32-25° F - Thin hexagonal plates (1)
• 25-21° F - Needles (2)
• 21-14° F - Hollow columns (3) (1)
• 14-10° F - Sector plates (4) (2)
• 10-3° F - Dendrites (5)
  
  

this is actually a radiating dentrite (above)

Variables

one of the variables is the humidity in the environment in wich the snow is being created in. that is a independatnt variable. the dependant variable is the result or the shape of the snow flake.

Hypotheses

My hypothesis is that in the more humid environment will create snowflakes that are bigger and sharper and form faster than the ones that are formed in a lower humidity environment.

Experimental Design

I am going to test the the forming of snow crystals on a copper wire. There will be one low humidity test and one higher humidity.to introduce higher humidity I will add water vapor to the atmosphere where the snow flakes are forming.
It took some trial and error to get the microscope to focus but eventually I put it inside my specially insulated fish tank so that way I could get the microscope to focus on the snow that was forming. The snow crystals needed something to form on I tried using a dime but it was not thin enough so I took apart a copper wire and used those strands of wire that were about the thickness of a hair. So then I got some dry ice and put it on a glass slide so that it was easy to put it under the microscope. The dry ice was on the slide, I then carefully put the wires on the dry ice and put it under the microscope. I watched the snowflakes begin to form. The First time I grew the snowflakes it was low humidity,32% to 33% the snow was forming in bunches where the wire was very near the dry ice.The second trial was I altered the environment. I used some water vapor to introduce more humidity. I put the dry ice on the slide and then I set the copper wire on the top, placed it under the microscope and watched them form. The Humidity was higher and the snowflakes formed faster.

Significant Observations

Results

Discussion

Essentially what happened was expected the wire over the dry ice snow formed on it. There were some differences in the results. The whole experiment was set up and then I got the dry ice and then I placed it under the microscope. The snowflakes started forming instantly because the dry ice is about negative one-hundred degrees Fahrenheit, because it is frozen carbon dioxide. In the environment with less humidity I expected the snowflakes to form smaller than and not as sharp as the ones that were formed in the lower humidity. The snow formed slower because there was less water vapor in the air for the dry ice to freeze. The snowflakes were smaller and there were less of them and they were smaller as I expected. With the humidity up more towards a room level of 50% I expected the snowflakes to form faster that the ones before and to be sharper and more numerous. The snowflakes that formed were indeed sharper and more numerous, they also formed faster than the ones before. The snow was definitely different than the trial before. The third time I increased the humidity up to 70% percent and I expected the snowflakes to be very sharp and there would be tons of them covering every inch of the wire. The snowflakes
were significantly larger and sharper than both the trials before and they were many more of them, completely covering the wire. This was more than I expected because the one before was not as numerous as this one and because an 18% percent change from 32% to 50% did not bring changes as significant.
There were some obstructions as I was trying to do the experiment, some minor and some creating problems. A major one was I discovered just how hard it is to control variables that you do not know about. It is also hard to prepare for things that I had no idea about. There were many variables that were not seen. Things that were overlooked were the temperature of dry ice because it is important because it is the temperature that the snow is forming at. Another problem was classifying the crystals because the microscope was not able to zoom in close enough to the snow it made that process difficult. Another problem was graphing the data because I had the humidity to go by but I needed to find another variable so I could make a graph of the data. But I did not have another variable so I had to make a table of results.
There overall experiment could use a fair amount of improvement. The process that the snowflakes form in needs to be changed because instead of supercooling the water vapor around the dry ice. Instead I would use the dry ice to cool the atmosphere below freezing and then I would put a wire under the microscope and then the snow would form at a realistic temperatures instead of negative 100 degrees Fahrenheit. Another thing that I would improve would be to make sure that the photographs were taken in the same place so that I could accurately compare the snowflakes that were formed in the different temperatures. The other things that I would improve would be more accurate temperature and humidity readings and being able to adjust the microscope without the conditions inside the chamber being altered. In conclusion, the experiment could be improved and modified in order to get more accurate results and to make it easier to apply the data to a realistic scenario. The experiment was interesting and and I got some good information out of it but it was hard to show other people.

Conclusion

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References

[[http://www.its.caltech.edu/~atomic/snowcrystals/class/class.htmhttp://www.sciencemaster.com/jump/physical/snowflakes.php|